Abstract:
The room temperature magnetoeletric coupling was investigated thoroughly in
various multiferroic (1-x)Ba0.985D0.015Zr0.10Ti0.90O3+xNi0.48Cu0.12Zn0.40Gd0.04Fe1.96O4
[(1-x)BDZT+xNCZGF] (where D = Ca, Sr) composites. Ferroelectric and ferrite
phase of the composites have been prepared by the standard solid state reaction
technique. Structural study was conducted by the X-ray diffraction (XRD) and the
Rietveld refinement was adopted for further analysis of the structure. The refined
XRD patterns confirmed all composites having a biphasic perovskite-spinel structure
with P4mm and Fd 3m space group. Microstructural characteristics of all samples
have been analyzed using Field Emission Scanning Electron Microscopy images.
The magnetoeletricaly coupled composites is illustrated by an obvious modification
in lattice, dielectric, ferroelectric and magnetic properties as a function of ferrite
content. Frequency dependence of the dielectric constant exhibits dispersion, which
can be modeled using a modified Debye function that considers the probability of
several ions contributing to the relaxation. The dielectric constant of the composites
was found to decrease with the addition of ferrite content in line with the theoretical
estimations of the Bruggeman, Maxwell-Garnett, Lichtencker and Looyenga models.
The dielectric constant and initial permeability were calculated theoretically using
the different models and compared with the experimental values. The discrepancy
between the calculated and experimental values of dielectric constant and initial
permeability might be attributed to the diffusion of ions and interaction between two
phases of the composites. The ac conductivity analysis revealed that the conduction
mechanism is attributed to the small polaron hopping and also obeyed the Jonscher‟s
power law. Complex impedance was evaluated using the Nyquist plot which ensured
the dominance of both grain and grain boundary resistances. Magnetic studies show
an enhancement of initial permeability, relative quality factor and saturation
magnetization, whereas magnetic loss gradually reduces with the increment of ferrite
content. The P-E hysteresis loops ensure the typical ferroelectric nature at room
temperature for x 0.20. The simultaneous P-E and M-H hysteresis loops confirm
the magnetoelectric coupling between ferroelectric and ferrite phases. Furthermore,
the maximum magnetoelectric response ~173 mV/(cm Oe) and ~194 mV/(cm Oe)
were found for 0.9BCZT+0.1NCZGF and 0.9BSZT+0.1NCZGF composite that
could be utilized in the future multifunctional devices.
